Life Begins

Chapter Four: Unicellular Life Forms on Shalimar

Shalimar offers a hospitable environment for life forms. The
warm, even temperatures of the shallow seas provide conditions
that support chemical reactions. Once rain had washed a rich mix
of chemicals into the water, the stage was set for the beginning
of life.

It
is not known whether life appeared more than once on Shalimar.
If there were a period without catastrophic meteor impacts, there
might have been time for life to begin and spread over most of
the warm parts of the planet, thus ensuring its own survival through
occasional local meteor bombardments.

Life probably began with a sort of fermentation
of the chemical mixture in the sea. Life forms somewhat similar
to earthly viruses still exist, and cells with cell walls and
nuclei exist in abundance. There are also cells without nuclei.
Fortunately for the future of life on the planet, chloroplasts
developed and were incorporated in cells to provide life forms
with a sustainable source of energy. Photosynthesis resulted in
the production of oxygen, which eventually changed the characteristics
of Shalimar's atmosphere.

Cells
on Shalimar reproduce by division. Sometimes the nucleus divides
but the cell itself does not complete division into two individual
cells. This doubling and sometimes redoubling of the chromosomes
leads to variation among the life forms. Not all of these cells
are viable, of course, but some survive. The proto-animals (cells
that eat other cells) engulf other cells to devour them, but occasionally
incorporate parts of the captive cell's DNA into their own. These
stratagems have proven to be so successful that sexual reproduction
is rare among these life forms.

On
Shalimar, survival is challenged by the occurrence of unpredictable
and possibly disastrous meteor strikes. Sudden temperature changes
and extended periods of darkness may radically change the environment
for the life forms on the planet. As there is no warning, and
as the strikes do not occur at regular intervals, preparation
for them is virtually impossible.

Microscopic life forms have become able
to deal with sudden changes by quickly forming tough shell walls.
The essential components of the cells remain inside these tough
membranes while life functions become dormant. When warmth and
light return, some of the cells are able to resume activity. The
environment selects for life forms capable of shutting down quickly
and surviving indefinite periods of dormancy.